Ecological quality assessment of Anzali wetland for heavy metals using heavy metals pollution index (HPI)

Research has shown that assessing the toxicity and ecological risk of various types of pollutants, including heavy metals, using specific indicators, is indispensable in the ecological risk assessment of the ecosystem. Accordingly, the aim of this study was the assessment of the ecological effect of heavy metals presence (Pb, Zn, Cu, Cd and, As) in Anzali wetland using Heavy Metals Pollution Index (HPI). 43 water samples were collected from the eastern, western and central parts of Anzali wetland. The samples were transferred to the laboratory, and the preparation steps were carried out using the ASTM method. Concentration of the elements was determined by Inductively Coupled Plasma -Atomic Emission Spectroscopy (ICP-AES). According to the concentration of heavy metals in the water samples, the index (HPI) was calculated. The results of the HPI index were classified into three classes: low risk (<15), moderate (15-30), and high risk (> 30). The numerical value of the HPI index was 3.59-23.3 with an average of 27.97, indicating the average level of heavy metals pollution in Anzali wetland. Indicator (HPI) in the eastern part of Anzali wetland and ​​the Pirbazar area showed a severe contamination and ecological hazard of the heavy metals and in the Abkenar region showed an acceptable ecological status. Although the average of HPI in the whole Anzali wetland was modest, but at some stations, especially in the east of the wetland, the HPI indicates the occurrence of ecological hazards in the wetland in the event of uncontrolled entry of pollutants in future. Therefore, monitoring the sources of these pollutants entering to the wetland and controlling the ecological risks is necessary.